/*
 * Copyright DataStax, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

"use strict";
const sinon = require('sinon');
const assert = require('assert');

const StreamIdStack = require('../../lib/stream-id-stack');

describe('StreamIdStack', function () {
  let clock;

  before(() => clock = sinon.useFakeTimers());
  after(() => clock.restore());

  this.timeout(2000);
  it('should pop and push', function () {
    const stack = newInstance();
    assert.strictEqual(stack.pop(), 0);
    assert.strictEqual(stack.pop(), 1);
    assert.strictEqual(stack.pop(), 2);
    assert.strictEqual(stack.inUse, 3);
    //1 becomes available again
    stack.push(1);
    assert.strictEqual(stack.inUse, 2);
    assert.strictEqual(stack.pop(), 1);
    stack.clear();
  });
  it('should not use more than allowed by the protocol version', function () {
    [
      [1, 128],
      [2, 128],
      [3, Math.pow(2, 15)]
    ].forEach(function (value) {
      const version = value[0];
      const maxSize = value[1];
      const stack = newInstance(version);
      const ids = pop(stack, maxSize + 20);
      assert.strictEqual(ids.length, maxSize + 20);
      for (let i = 0; i < maxSize + 20; i++) {
        if (i < maxSize) {
          assert.strictEqual(ids[i], i);
        }
        else {
          assert.strictEqual(ids[i], null);
        }
      }
      stack.push(5);
      assert.strictEqual(stack.inUse, maxSize - 1);
      stack.clear();
    });
  });
  it('should yield the lowest available id', function () {
    const stack = newInstance(3);
    const ids = pop(stack, 128 * 3 - 1);
    assert.strictEqual(ids.length, 128 * 3 - 1);
    for (let i = 0; i < ids.length; i++) {
      assert.strictEqual(ids[i], i);
    }
    //popped all from the first 3 groups
    assert.strictEqual(stack.pop(), 128 * 3 - 1);
    assert.strictEqual(stack.groups.length, 3);
    stack.push(10); //group 0
    stack.push(200); //group 1
    assert.strictEqual(stack.pop(), 10);
    assert.strictEqual(stack.pop(), 200);
    assert.strictEqual(stack.pop(), 128 * 3);
    stack.push(200);
    assert.strictEqual(stack.pop(), 200);
    assert.strictEqual(stack.groups.length, 4);
    stack.clear();
  });
  it('should release unused groups', function () {
    const releaseDelay = 5000;
    const stack = newInstance(3, releaseDelay);
    //6 groups,
    const length = 128 * 5 + 2;

    pop(stack, length);
    assert.strictEqual(stack.inUse, length);

    // return just 1 to the last group
    stack.push(128 * 5);
    assert.strictEqual(stack.groups.length, 6);

    //the last group is completed and can be released
    stack.push(128 * 5 + 1);

    // push 10 more
    push(stack, 0, 10);

    assert.strictEqual(stack.groups.length, 6);

    clock.tick(releaseDelay);

    //there should be 5 groups now
    assert.strictEqual(stack.groups.length, 5);

    assert.strictEqual(stack.inUse, length - 12);

    stack.clear();
  });
  it('should not release the current group', function () {
    const releaseDelay = 100;
    const stack = newInstance(3, releaseDelay);

    //6 groups,
    pop(stack, 128 * 5 + 2);
    //return just 1 to the last group
    stack.push(128 * 5);
    assert.strictEqual(stack.groups.length, 6);
    //the last group is completed and but can not be released as is the current one
    stack.push(128 * 5 + 1);
    assert.strictEqual(stack.groups.length, 6);

    clock.tick(releaseDelay);

    //there should be 5 groups now
    assert.strictEqual(stack.groups.length, 6);
    stack.clear();
  });
  it('should not release more than release size per time', function () {
    const releaseDelay = 100;
    const stack = newInstance(3, releaseDelay);
    //12 groups,
    pop(stack, 128 * 11 + 2);
    assert.strictEqual(stack.groups.length, 12);
    //return
    push(stack, 0, 128 * 11 + 2);
    assert.strictEqual(stack.groups.length, 12);
    assert.strictEqual(stack.groupIndex, 0);
    assert.strictEqual(stack.inUse, 0);
    assert.strictEqual(stack.pop(), 127); //last from the first group
    assert.strictEqual(stack.inUse, 1);

    clock.tick(releaseDelay);

    //there should be 12 - 4 groups now
    assert.strictEqual(stack.groups.length, 8);

    clock.tick(releaseDelay);

    //there should be 12 - 8 groups now
    assert.strictEqual(stack.groups.length, 4);
    stack.clear();
  });
});

/** @returns {StreamIdStack}  */
function newInstance(version, releaseDelay) {
  const stack = new StreamIdStack(version || 3);
  stack.releaseDelay = releaseDelay || 100;
  return stack;
}

function pop(stack, n) {
  const arr = [];
  for (let i = 0; i < n; i++) {
    arr.push(stack.pop());
  }
  return arr;
}

function push(stack, initialValue, length) {
  if (Array.isArray(initialValue)) {
    initialValue.forEach(stack.push.bind(stack));
    return;
  }
  for (let i = 0; i < length; i++) {
    stack.push(initialValue + i);
  }
}